How to Machine Aerospace-Grade Composites

A research team at Loughborough University in the UK has come up with a method for machining aerospace-grade, carbon fiber-reinforced composites. The method is based on a device that uses ultrasound to help soften the carbon composite material in the area being worked. It also works on high-strength aerospace alloys.

The research team is headed by Vladimir Babitsky, a professor in the university's Wolfson School of Mechanical and Manufacturing Engineering, who invented the technique. During the last several years, he's been developing the method along with senior lecturer Anish Roy and professor Vadim Silberschmidt.

The ultrasonically assisted machining (UAM) device combines a traditional turning, drilling, or milling machine with a specially designed piezoelectric transducer. It creates ultrasonic vibrations at frequencies between 20 kHz and 39 kHz. This ultrasound-assisted cutting technique makes the composite, which is usually quite stiff and brittle, so soft that less force is needed. Consequently, far less damage is done to the material.

Loughborough University researchers have come up with a method for machining aerospace-grade, carbon fiber-reinforced composites using an ultrasonically assisted machining device. Team memberAnish Roy uses the device to drill composites.(Source: Loughborough University)

Roy said in a press release that, at least in the laboratory, the UAM device has made it much easier to cut aerospace alloys and composites. "It is like cutting through butter."

Any kind of machining can damage composites, Roy said, but the UAM technique causes far less damage, generates less waste, and results in a better finish. The team's challenge is to reduce damage even further by reducing drilling force even more. Vaibhav Phadnis, who worked on a doctoral project in UAM while at the university and more recently has been working with Airbus, said in the release that the device's cost-effectiveness and easy setup and use make the technology attractive for aerospace manufacturing processes.

He and Farrukh Makhdum, a fellow doctoral student, helped refine the drilling technique used on carbon fiber composites. They published their work last year in an article also authored by Roy and Silberschmidt in the journal Composites Part A: Applied Science and Manufacturing. Phadnis is now a project engineer at Sheffield University's Advanced Manufacturing Research Centre.

Aerospace isn't the only place where UAM can be used. It's also being applied to biomedical applications -- for example, for drilling holes in bones before orthopedic surgery -- and it is showing promise for drilling very small holes in printed circuit boards for high-precision component assembly.

RalphyBoy, thanks for the followup info. That makes total sense. As the Loughborough U researchers note, UAM is not new but their tweaks on it are. Re the need for shop glasses, you'd be surprised how many people have written us about that photo.Unfortunately for the rest of us, we've had to block the use of URLs because of problems with spammers. Fortunately, we can all still Google company/product/technology names :)

Thanks for all those good questions, Clinton. As I mentioned to Lou below, the softening appears to be temporary and hardness is not affected after the ultrasound is removed. So I'd bet that the use of this technique for weapons would have to use a lot of sustained energy to be effective. But that's a very scary scenario, and you may be on to something. I, too, wish the researchers had been more forthcoming about the details of their process. The answers to your questions might be in the open access article we give a link to.

Interesting tangent that the discussion has taken, one that could probably last for a few years. And use up a lot of pitchers of beer.

But getting back to the article, I'm curious about the structural integrity of the area to which the ultrasonic vibration was applied.

As Jim pointed out, ultrasonic welding can occur because of the softening of the plastic subjected to the vibration. At least, this is how it happens when dealing with thermoplastics that can be heated and cooled multiple times with little degradation of the material properties (assuming you don't regrind them).

Most structural carbon fibre composites are not thermoplastics, however, but thermosets. These materials undergo a one-direction hardening - they can't be softened again by heat or vibration. So using ultra-sonic vibration to "soften" these materials must be using a different modality of softening than ultra-sonic welding uses to melt thermoplastics.

Also, the carbon fibre is usually laid down in sheet form, in very specific patterns. If the ultrasonic vibration can locally "soften" the carrier material, can the carbon fibers move or shift while the carrier is soft?

Good engineering type questions, but my initial thought when reading the article was actually in a totally different direction - if carbon fibre reinforced composites can be softened with ultrasonic vibration, couldn't this lead to weapons capable of penetrating or softening panels on armored vehicles or airplanes, for instance? Carbon fibre composites are being used to replace steel as structural members in so many products... could all these applications be at risk to an ultra-sonic gun (soon to be invented, of course)?

JimT, I agree--I don't think what we're talking about is all decisions coming from the top. I think we're talking about *uninformed* decisions made from higher up the hierarchy that don't reflect knowledge and understanding of either those lower down the hierarchy, or of information coming from outside the company. The difference between the to can clearly be illustrated by companies with people at the top who do understand their markets/customers/general economic conditions and changes in all of those. One of the most famous recent examples in the latter category is Steve Jobs. An older one is Lee Iacocca's famous turnaround at Chrysler.

I think your point is that decisions coming from the top management are not always the best and wisest decisions. (What happened to Detroit in the 80's:Exactly) To clarify my earlier comment that companies often act only on suggestions that come from the top did not mean those decisions coming were the GOOD decisions.Too many Corporate dealings are polluted with Yes-Men following bad orders.

JimT, I don't think that's true all the time. But as a consumer, I do see it occurring a lot of the time. Also, I just finished a very interesting (and very long) book written back in 1989 called The Reckoning by David Halberstam. It covers the Detroit car industry and how it completely missed what was going on in the economy, the oil business, and among consumers that allowed the Japanese car industry to succeed. It's absolutely fascinating, and basically takes a deep inside look at Nissan and Ford during those years.

Unfortunately, I think you are right.My direct experience with big corporate entities is that they are all very two-sided.One face advertises openness and willingness to meet market demands, while the other face categorically rejects inputs & suggestions unless they come from the top of their management chain. Ironic.

JimT, that sounds like an interesting business, and probably with its own frustrations as well. My issue is a little different--I want to give feedback about improvements to the manufacturers of products or systems already in use. I don't want to make money by designing something, I just want my user feedback received by the right people who can do something with it. There don'tseem to be any clear avenues for doing that.

Ann, you've just described the bottle neck that I am trying to help people with; how to get the ideas going.Since I started an independent design consultation service, I get lots of little quirky ideas. Clients range from individual inventors, to small corporate entities and start-ups.But the effort is the same; trying to put ideas into realistic embodiments.

Industrial workplaces are governed by OSHA rules, but this isn’t to say that rules are always followed. While injuries happen on production floors for a variety of reasons, of the top 10 OSHA rules that are most often ignored in industrial settings, two directly involve machine design: lockout/tagout procedures (LO/TO) and machine guarding.

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